Werner syndrome (WS) is an uncommon autosomal recessive disease characterized by premature aging and genetic instability, and associated with a high incidence of specific, uncommon cancers. The gene mutated in WS, WRN, belongs to the family of RecQ helicases and encodes both 3' -> 5' DNA helicase and 3" -> 5' DNA exonuclease activities. Biochemical studies indicate that the helicase preferentially unwinds DNA harboring alternative structures and that the exonuclease preferentially excises mismatched nucleotides at the 3'-terminus. Cloning and purification of WRN affords us the opportunity to study its biochemistry in detail and use these findings in concert with other projects in this program to understand how the wild-type WS protein, WRN, suppresses genetic instability and cancer. In order to gain insights into the in vivo fianctions of the WS protein, we will 1. identify and characterize proteins that interact physically and functionally with WRN, and 2. establish model in vitro systems to determine the involvement of WRN in cross-link repair. In addition, we will examine WRN single nucleotide polymorphJsms in the general population for functional effects, and analyze polymorphic variants and WRN mutations in cancers associated with WS, in particular, sarcomas. These studies will provide the biochemical foundation for the proposed program project.